编写的代码如下，就是启动 APP 的代码

public class DinnerTest {
    public static void main(String[] args) throws MalformedURLException {

        DesiredCapabilities cap = new DesiredCapabilities();
        cap.setCapability("deviceName", "emulator-5554");
        cap.setCapability("automationName", "Appium");
        cap.setCapability("platformName", "Android");
        cap.setCapability("platformVersion", "7.1.1");

        cap.setCapability("appPackage", "com.android.calculator2");
        cap.setCapability("appActivity", "calculator2");

        AppiumDriver driver = new AndroidDriver<>(new URL("http://127.0.0.1:4723/wd/hub"), cap);
    }
}

错误日志如下：

Exception in thread "main" org.openqa.selenium.WebDriverException: It is impossible to create a new session because 'createSession' which takes HttpClient, InputStream and long was not found or it is not accessible
Build info: version: '3.12.0', revision: '7c6e0b3', time: '2018-05-08T15:15:08.936Z'
System info: host: 'VincentdeMacBook-Pro.local', ip: 'fe80:0:0:0:10b5:6690:b81:6ae2%en0', os.name: 'Mac OS X', os.arch: 'x86_64', os.version: '10.14', java.version: '1.8.0_181'
Driver info: driver.version: AndroidDriver
    at io.appium.java_client.remote.AppiumCommandExecutor$1.createSession(AppiumCommandExecutor.java:182)
    at io.appium.java_client.remote.AppiumCommandExecutor.createSession(AppiumCommandExecutor.java:196)
    at io.appium.java_client.remote.AppiumCommandExecutor.execute(AppiumCommandExecutor.java:218)
    at org.openqa.selenium.remote.RemoteWebDriver.execute(RemoteWebDriver.java:543)
    at io.appium.java_client.DefaultGenericMobileDriver.execute(DefaultGenericMobileDriver.java:42)
    at io.appium.java_client.AppiumDriver.execute(AppiumDriver.java:1)
    at io.appium.java_client.android.AndroidDriver.execute(AndroidDriver.java:1)
    at org.openqa.selenium.remote.RemoteWebDriver.startSession(RemoteWebDriver.java:207)
    at org.openqa.selenium.remote.RemoteWebDriver.<init>(RemoteWebDriver.java:130)
    at io.appium.java_client.DefaultGenericMobileDriver.<init>(DefaultGenericMobileDriver.java:38)
    at io.appium.java_client.AppiumDriver.<init>(AppiumDriver.java:84)
    at io.appium.java_client.AppiumDriver.<init>(AppiumDriver.java:94)
    at io.appium.java_client.android.AndroidDriver.<init>(AndroidDriver.java:88)
    at com.Dinner.Test.DinnerTest.main(DinnerTest.java:28)
Caused by: java.lang.reflect.InvocationTargetException
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at io.appium.java_client.remote.AppiumCommandExecutor$1.createSession(AppiumCommandExecutor.java:172)
    ... 13 more
Caused by: org.openqa.selenium.WebDriverException: An unknown server-side error occurred while processing the command. Original error: Cannot start the 'com.android.calculator2' application. Visit https://github.com/appium/appium/blob/master/docs/en/writing-running-appium/android/activity-startup.md for troubleshooting. Original error: Cannot start the 'com.android.calculator2' application. Visit https://github.com/appium/appium/blob/master/docs/en/writing-running-appium/android/activity-startup.md for troubleshooting. Original error: Activity name '.calculator2' used to start the app doesn't exist or cannot be launched! Make sure it exists and is a launchable activity
Build info: version: '3.12.0', revision: '7c6e0b3', time: '2018-05-08T15:15:08.936Z'
System info: host: 'VincentdeMacBook-Pro.local', ip: 'fe80:0:0:0:10b5:6690:b81:6ae2%en0', os.name: 'Mac OS X', os.arch: 'x86_64', os.version: '10.14', java.version: '1.8.0_181'
Driver info: driver.version: AndroidDriver
remote stacktrace: UnknownError: An unknown server-side error occurred while processing the command. Original error: Cannot start the 'com.android.calculator2' application. Visit https://github.com/appium/appium/blob/master/docs/en/writing-running-appium/android/activity-startup.md for troubleshooting. Original error: Cannot start the 'com.android.calculator2' application. Visit https://github.com/appium/appium/blob/master/docs/en/writing-running-appium/android/activity-startup.md for troubleshooting. Original error: Activity name '.calculator2' used to start the app doesn't exist or cannot be launched! Make sure it exists and is a launchable activity
    at getResponseForW3CError (/Applications/Appium.app/Contents/Resources/app/node_modules/appium/node_modules/appium-base-driver/lib/protocol/errors.js:826:9)
    at asyncHandler$ (/Applications/Appium.app/Contents/Resources/app/node_modules/appium/node_modules/appium-base-driver/lib/protocol/protocol.js:404:37)
    at tryCatch (/Applications/Appium.app/Contents/Resources/app/node_modules/appium/node_modules/babel-runtime/regenerator/runtime.js:67:40)
    at GeneratorFunctionPrototype.invoke [as _invoke] (/Applications/Appium.app/Contents/Resources/app/node_modules/appium/node_modules/babel-runtime/regenerator/runtime.js:315:22)
    at GeneratorFunctionPrototype.prototype.(anonymous function) [as next] (/Applications/Appium.app/Contents/Resources/app/node_modules/appium/node_modules/babel-runtime/regenerator/runtime.js:100:21)
    at GeneratorFunctionPrototype.invoke (/Applications/Appium.app/Contents/Resources/app/node_modules/appium/node_modules/babel-runtime/regenerator/runtime.js:136:37)
    at <anonymous>
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
    at org.openqa.selenium.remote.W3CHandshakeResponse.lambda$new$0(W3CHandshakeResponse.java:57)
    at org.openqa.selenium.remote.W3CHandshakeResponse.lambda$getResponseFunction$2(W3CHandshakeResponse.java:104)
    at org.openqa.selenium.remote.ProtocolHandshake.lambda$createSession$0(ProtocolHandshake.java:123)
    at java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:193)
    at java.util.Spliterators$ArraySpliterator.tryAdvance(Spliterators.java:958)
    at java.util.stream.ReferencePipeline.forEachWithCancel(ReferencePipeline.java:126)
    at java.util.stream.AbstractPipeline.copyIntoWithCancel(AbstractPipeline.java:498)
    at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:485)
    at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:471)
    at java.util.stream.FindOps$FindOp.evaluateSequential(FindOps.java:152)
    at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
    at java.util.stream.ReferencePipeline.findFirst(ReferencePipeline.java:464)
    at org.openqa.selenium.remote.ProtocolHandshake.createSession(ProtocolHandshake.java:126)
    ... 18 more

不知道问题是啥～谢谢各位了～查了好久